Describe Data structures used during passes of assembler and their use.

During passes of assembler, the Data structures define as:

Pass 1 data base

• Input source program
• A location counters (LC)
• A machine-operation table (i.e. MOT), which indicates the symbolic mnemonic for each instruction and instruction's length.
• Pseudo- operation table
• Symbol table
• Literal table
• Copy of the input to be used later through pass 2

Pass 2

• Coping of source program input to pass 1
• Location counter (LC)
• MOT
• POT
• ST
• Base table which indicates that registers are currently identified as base register.
• A work space, INST, which used to hold instruction as its different parts are being assembled together
• Punch line, utilized to produce a printed listing.
• Punch card used for converting assembled instructions in the format required by the loader.